VelosplitWatts per kg calculator
Divide your FTP by your body weight to get your power-to-weight ratio in watts per kilogram, then see where it sits on Andrew Coggan's power profile chart. W/kg is the number that decides who gets up a climb first, and, as the physics below shows, much less of what happens on the flat.
Power to weight
3.33 W/kg
On Coggan's power profile chart
Moderate (3.08 to 3.65 W/kg)
The formula
W/kg = FTP ÷ body weight. FTP, functional threshold power, is roughly the highest average power you can hold for about an hour, in watts. Use your body weight in kilograms without the bike, which is the convention the chart below uses. A rider with an FTP of 250 W who weighs 75 kg is at 3.33 W/kg.
W/kg chart
These bands are the functional-threshold column of Coggan's power profile chart [1, 2]. He built it as a straight-line scale between two anchors: the world record holder, at 6.60 W/kg for men and 5.69 W/kg for women, and the average untrained person, at 2.22 and 1.83. Every row of the original steps by the same amount. It is a ranking scale for comparing riders, not a survey of how riders are distributed.
| Category | Men (W/kg) | Women (W/kg) |
|---|---|---|
| World class | 5.93 to 6.60 | 5.10 to 5.69 |
| Exceptional | 5.36 to 5.93 | 4.60 to 5.10 |
| Excellent | 4.79 to 5.36 | 4.10 to 4.60 |
| Very good | 4.22 to 4.79 | 3.59 to 4.10 |
| Good | 3.65 to 4.22 | 3.09 to 3.59 |
| Moderate | 3.08 to 3.65 | 2.59 to 3.09 |
| Fair | 2.51 to 3.08 | 2.08 to 2.59 |
| Novice 2 | 1.93 to 2.51 | 1.58 to 2.08 |
| Novice 1 | 1.27 to 1.93 | 0.99 to 1.58 |
In the original chart neighbouring categories overlap by a few rows. The boundaries here are the chart's own bold rows, which sit inside those overlaps, so every value falls in one category.
Why W/kg matters on climbs, not on the flat
On a climb, most of your power goes into lifting your mass against gravity, and that force grows with weight. On the flat, most of it goes into pushing air aside, and that force depends on your CdA and speed, not your weight; mass only enters through rolling resistance. So the same watts from a lighter rider buy a lot of speed uphill and very little on the flat. The planner's physics shows it directly.
Take two riders, both producing 250 W, with the same CdA of 0.339 m², one at 75 kg and one at 65 kg. On flat ground in still air, the heavier rider holds 35.8 km/h and the lighter 36.0 km/h, only 0.7 percent faster. Up a 5 km climb at 8 percent, the heavier rider takes 24:23 and the lighter 21:45: 12.1 percent faster, for the same 250 W.
That is why climbers chase W/kg and time triallists chase CdA. On a flat course, the CdA estimator tells you more than this page does.
Limitations
The result is only as good as your FTP. A number from an old or short test can put you a whole category out. The chart is also a ranking scale for trained riders built between two anchors, so the category names describe where you sit on that scale, not a racing licence or your age group. And W/kg alone does not predict a race: on a rolling course, CdA, pacing and how you ride the descents all matter too.
To turn your FTP and weight into a target wattage for every part of a real course, use the race power planner. The equations behind both are on the methodology page.
References
- Coggan A. Power profiling. TrainingPeaks. trainingpeaks.com/learn/articles/power-profiling
- Allen H, Coggan A. Training and Racing with a Power Meter. VeloPress.